Operating Modes

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

Following are paragraphs that briefly describe the operation of each of the rear wiper and washer system operating modes.

Intermittent Wipe Mode - When the right (wiper) multifunction switch control sleeve is moved to the Delay (Intermittent) position, the microcontroller within the SCCM sends an electronic rear wiper switch on status message to the BCM over the CAN data bus. The BCM responds by energizing a High Side Driver (HSD) that directs battery current to the rear wiper motor. If the front wiper system is inactive, the BCM will cycle the rear wiper at a fixed intermittent speed. If the front wiper system is active, the BCM cycles the rear wiper in a synchronous manner, at one-half the speed of the front wipers. If Reverse (R ) has been selected with the transmission gear selector, the BCM operates the rear wiper in a continuous manner.
When the Off position of the right multifunction switch control sleeve is selected, the SCCM microcontroller sends an electronic rear wiper switch off status message to the BCM over the CAN data bus. The event that occurs depends upon the position of the wiper blade on the liftgate glass at the moment that the control sleeve Off position is selected.

If the rear wiper blade is in the down position on the glass when the Off position is selected, the park switch that is integral to the rear wiper motor is an open circuit, which provides a hard wired park switch sense input to the BCM. The internal BCM circuitry pulls the park switch sense input to ground when the switch is open so that the microcontroller sees a ground when the wiper blade is parked. The BCM then de-energizes the rear wiper motor and the wiper motor ceases to operate.

If the rear wiper blade is not in the down position on the liftgate glass at the moment the Off position is selected, the park switch is closed to fused ignition output and the BCM continues running the wiper motor at low speed until the rear wiper blade is in the down position on the liftgate glass and the park switch input to the BCM is again pulled to ground.
Wash Mode - When the control stalk of the right (wiper) multifunction switch is pushed forward to the momentary rear Wash position, the SCCM microcontroller sends an electronic washer switch status message to the BCM. Then the BCM directs battery current and ground to the washer pump/motor. This will cause the washer pump/motor to be energized for as long as the switch is held closed (up to approximately 20 seconds) and to be de-energized when the control stalk is released.
When the control stalk is pushed forward to the momentary Wash position while the rear wiper system is operating the washer pump/motor operation is the same. However, the BCM logic also overrides the selected wiper operating mode and operates the wiper motor in a continuous low speed mode for as long as the control stalk is held in the momentary Wash position, then reverts to the selected operating mode several wipe cycles after the control stalk is released. If the Wash switch is held closed for more than about 20 seconds, the BCM will suspend washer pump/motor operation until the control stalk is released for about 2 seconds, then cycled back to the Wash position.
Wipe-After-Wash Mode - When the control stalk of the right (wiper) multifunction switch is pushed forward to the momentary rear Wash position for more than about one-half second while the rear wiper system is not operating, the BCM directs battery current and ground to the washer pump/motor and energizes the rear wiper motor in a continuous mode for as long as the switch is held closed. When the control stalk is released, the BCM de-energizes the washer pump/motor immediately, but allows the rear wiper motor to operate for about three additional wipe cycles. An additional wipe cycle is performed about six seconds later before the BCM de-energizes the rear wiper motor and parks the wiper blade near the base of the liftgate glass.
The BCM monitors the changing state of the wiper motor park switch through a hard wired wiper park switch sense circuit input. This input allows the BCM to monitor the number of wipe cycles that occur after the control stalk is released, and to determine the proper interval at which to de-energize the wiper motor to complete the Wipe-After-Wash mode cycle.